Yarn tubes have long been provided for use on winders and such have usually been of paper. Such yarn tubes are of standard lengths from of 61/2 inches, 81/2 inches and 13 inches having an approximate inside diameter of 31/4 inches. It has been found in connection with use on winders such as a Leesona 959 winder that such tubes possess substantial disadvantages in that there is not sufficient crushing strength of the tube to accommodate large packages of polypropylene slit type yarn and the like because such will crush or distort inwardly so as to prevent regular doffing of the package from the spindle of the winder. Such spindles are often constructed having circumferentially spaced ribs so that the dimensional stability of the tube carrying many convolutions of yarn thereon is of the utmost importance.
Prior to this invention phenolic or aluminum tubes have largely replaced the paper tubes in an attempt to eliminate these problems. Aluminum tubes bend if dropped and will not fit properly on winders. Phenolic tubes will not bend or break, but after yarn is cut off a number of times, these tubes will surface flake and end-chip off, and such cannot be recycled.
The manufacture of yarn carrier structures (bobbins, etc.) for winding various synthetic yarns is thus will known in the art and covers a range of manufacturing techniques, i.e. metal forming, hand lay up techniques, etc., which utilize an array of materials. Materials include aluminum, phenolics, various impregnated papers and cloth, and a range of thermoplastics. The nature of the yarn and winding process dictates the engineering qualities that a tube must possess, i.e. strength, rigidity, creep resistance, surface smoothness, temperature resistance, crush resistance, abuse (impact) resistance, etc., if the tube is to be successfully repeatably used as a textile yarn carrier structure.
Heretofore, the use of precision injection molded thermoplastic tubes or bobbins for repeated winding of yarns that have elastic properties and memory which result in imposing very severe time dependent compressive stresses on a bobbin as they are wound into a package has not been achieved. This problem is described in U.S. Pat. No. 3,002,872. Reference is also made to U.S. Pat. No. 3,167,263. Yarns which are capable of exerting severe winding tensions, i.e. 0.1 to 0.2 grms per denier are described in the industry as flat tape, monofilament, fibrillated and twisted yarns, respectively. These yarns are primarily manufactured from synthetic polypropylenes and polyamides (nylons) which require, due to the nature of the yarn, high winding tension to provide a useable tight self-contained package. The high winding tension results in an immediate compressive stress on the bobbin at the initiation of winding while at the same time it elastically stretches the yarn. During and subsequent to winding, the elastically stretched yarn attempts to recover its original relaxed state and this "yarn memory" imposes a time dependent compressive stress on the bobbin.
The use of injection molded foamed reinforced thermoplastic bobbins as suggested in West German Pat. No. 2,039,517 of 1972 as disposable bobbins for synthetic yarn winding, would not be suitable for repeated winding due to the extent of deformation occurring during the first winding and yarn relaxation process. Table 1 below lists engineering properties for one of the materials referred to in the West German patent against similar properties for materials used and included herein. The difference in rigidity, strength and creep rupture failure times of the two materials substantiates and supports the contention that bobbins which will see repeated use must be manufactured from specially selected and designed engineering materials.
The object of this invention is to provide a means by which the economical process of injection molding may be utilized to manufacture reuseable cost effective high tension bearing textile yarn carrier structures. It was found by experimentation that chemically coupled glass fiber reinforced thermoplastics, as sometimes used such as in pressure pipes, gears, and pump components had the necessary short term and long term engineering properties to be economically viable for the present structures. Dimensions of the tube were selected to be compatible with the material choice so that a utilitarian tube would result.
Accordingly, it is an important object of the present invention to provide an economical yarn tube having substantial strength to resist crushing.
Another important object of the invention is to provide tubes which are inexpensive and which may be recycled and possess strength against abrasion and misuse.
Such tubes are used for packaging yarn for positioning upon a creel to make beams. These tubes are also used for filling yarn on shuttleless looms. The most important use for the yarn tube of the present invention which is now envisioned is for use in winding slit yarn for use in carpet backing.
The prior art is typified by U.S. Pat. Nos. 2,945,638; 3,002,872; 3,643,888; 3,746,275; and 3,871,601. These patents show tubes of various constructions but none show the combination of particular dimension and material which has been provided to afford a recyclable yarn tube capable of withstanding substantial yarn crushing forces.